Question

i could not have hoped for a better decision. 这里的 could not have done的意思

Answer 1

“could+have+done”是虚拟语气,表示对过去事情的假设,意思是本来能够做某事而没有做.

例如:
He could have passed the exam,but he was too careless.本来他能够通过考试,但是他太粗心.

追答

所以could not have done的意思就是:本来不能够做的事，却做了。

例如：He couldn't have failed the exxam,and he studied hard recently.